Electrochemical Fabrication Method and Application for Producing Three-Dimensional Structures Having Improved Surface Finish

ABSTRACT

An electrochemical fabrication process produces three-dimensional structures (e.g. components or devices) from a plurality of layers of deposited materials wherein the formation of at least some portions of some layers are produced by operations that remove material or condition selected surfaces of a deposited material. In some embodiments, removal or conditioning operations are varied between layers or between different portions of a layer such that different surface qualities are obtained. In other embodiments varying surface quality may be obtained without varying removal or conditioning operations but instead by relying on differential interaction between removal or conditioning operations and different materials encountered by these operations.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No. 10/387,958 (Microfabrica Docket No. P-US050-A-MG), filed Mar. 13, 2003 which in turn claims the benefit of U.S. Provisional Patent Application No. 60/364,261 filed Mar. 13, 2002 and U.S. Provisional Application No. 60/379,130, filed May 7, 2002. All of these applications are hereby incorporated herein by reference as if set forth in full herein.

FIELD OF THE INVENTION

The present invention relates generally to the formation of three-dimensional structures (e.g. components or devices) using electrochemical fabrication methods via a layer-by-layer build up of deposited materials where at least some layers are subjected to surface conditioning processes and wherein the surface conditioning processes are varied to yield varying surface finishes between different portions of a single layer or between different layers or portions of different layers.

BACKGROUND

A technique for forming three-dimensional structures (e.g. parts, components, devices, and the like) from a plurality of adhered layers was invented by Adam L. Cohen and is known as Electrochemical Fabrication. It is being commercially pursued by Microfabrica® Inc. (formerly MEMGenCorporation) of Van Nuys, Calif. under the name EFAB®. This technique was described in U.S. Pat. No. 6,027,630, issued on Feb. 22, 2000. This electrochemical deposition technique allows the selective deposition of a material using a unique masking technique that involves the use of a mask that includes patterned conformable material on a support structure that is independent of the substrate onto which plating will occur. When desiring to perform an electrodeposition using the mask, the conformable portion of the mask is brought into contact with a substrate while in the presence of a plating solution such that the contact of the conformable portion of the mask to the substrate inhibits deposition at selected locations. For convenience, these masks might be generically called conformable contact masks; the masking technique may be generically called a conformable contact mask plating process. More specifically, in the terminology of Microfabrica Inc. such masks have come to be known as INSTANT MASKS™ and the process known as INSTANT MASKING™ or INSTANT MASK™ plating. Selective depositions using conformable contact mask plating may be used to form single layers of material or may be used to form multi-layer structures. The teachings of the '630 patent are hereby incorporated herein by reference as if set forth in full herein. Since the filing of the patent application that led to the above noted patent, various papers about conformable contact mask plating (i.e. INSTANT MASKING) and electrochemical fabrication have been published:

-   -   1. A. Cohen, G. Zhang, F. Tseng, F. Mansfeld, U. Frodis and P.         Will, “EFAB: Batch production of functional, fully-dense metal         parts with micro-scale features”, Proc. 9th Solid Freeform         Fabrication, The University of Texas at Austin, p161, August         1998.     -   2. A. Cohen, G. Zhang, F. Tseng, F. Mansfeld, U. Frodis and P.         Will, “EFAB: Rapid, Low-Cost Desktop Micromachining of High         Aspect Ratio True 3-D MEMS”, Proc. 12th IEEE Micro Electro         Mechanical Systems Workshop, IEEE, p244, January 1999.     -   3. A. Cohen, “3-D Micromachining by Electrochemical         Fabrication”, Micromachine Devices, March 1999.     -   4. G. Zhang, A. Cohen, U. Frodis, F. Tseng, F. Mansfeld, and P.         Will, “EFAB: Rapid Desktop Manufacturing of True 3-D         Microstructures”, Proc. 2nd International Conference on         Integrated MicroNanotechnology for Space Applications, The         Aerospace Co., April 1999.     -   5. F. Tseng, U. Frodis, G. Zhang, A. Cohen, F. Mansfeld, and P.         Will, “EFAB: High Aspect Ratio, Arbitrary 3-D Metal         Microstructures using a Low-Cost Automated Batch Process”, 3rd         International Workshop on High Aspect Ratio MicroStructure         Technology (HARMST'99), June 1999.     -   6. A. Cohen, U. Frodis, F. Tseng, G. Zhang, F. Mansfeld, and P.         Will, “EFAB: Low-Cost, Automated Electrochemical Batch         Fabrication of Arbitrary 3-D Microstructures”, Micromachining         and Microfabrication Process Technology, SPIE 1999 Symposium on         Micromachining and Microfabrication, September 1999.     -   7. F. Tseng, G. Zhang, U. Frodis, A. Cohen, F. Mansfeld, and P.         Will, “EFAB: High Aspect Ratio, Arbitrary 3-D Metal         Microstructures using a Low-Cost Automated Batch Process”, MEMS         Symposium, ASME 1999 International Mechanical Engineering         Congress and Exposition, November, 1999.     -   8. A. Cohen, “Electrochemical Fabrication (EFABTM)”, Chapter 19         of The MEMS Handbook, edited by Mohamed Gad-El-Hak, CRC Press,         2002.     -   9. “Microfabrication—Rapid Prototyping's Killer Application”,         pages 1-5 of the Rapid Prototyping Report, CAD/CAM Publishing,         Inc., June 1999.

The disclosures of these nine publications are hereby incorporated herein by reference as if set forth in full herein.

The electrochemical deposition process may be carried out in a number of different ways as set forth in the above patent and publications. In one form, this process involves the execution of three separate operations during the formation of each layer of the structure that is to be formed:

-   -   1. Selectively depositing at least one material by         electrodeposition upon one or more desired regions of a         substrate.     -   2. Then, blanket depositing at least one additional material by         electrodeposition so that the additional deposit covers both the         regions that were previously selectively deposited onto, and the         regions of the substrate that did not receive any previously         applied selective depositions.     -   3. Finally, planarizing the materials deposited during the first         and second operations to produce a smoothed surface of a first         layer of desired thickness having at least one region containing         the at least one material and at least one region containing at         least the one additional material.

After formation of the first layer, one or more additional layers may be formed adjacent to the immediately preceding layer and adhered to the smoothed surface of that preceding layer. These additional layers are formed by repeating the first through third operations one or more times wherein the formation of each subsequent layer treats the previously formed layers and the initial substrate as a new and thickening substrate.

Once the formation of all layers has been completed, at least a portion of at least one of the materials deposited is generally removed by an etching process to expose or release the three-dimensional structure that was intended to be formed.

The preferred method of performing the selective electrodeposition involved in the first operation is by conformable contact mask plating. In this type of plating, one or more conformable contact (CC) masks are first formed. The CC masks include a support structure onto which a patterned conformable dielectric material is adhered or formed. The conformable material for each mask is shaped in accordance with a particular cross-section of material to be plated. At least one CC mask is needed for each unique cross-sectional pattern that is to be plated.

The support for a CC mask is typically a plate-like structure formed of a metal that is to be selectively electroplated and from which material to be plated will be dissolved. In this typical approach, the support will act as an anode in an electroplating process. In an alternative approach, the support may instead be a porous or otherwise perforated material through which deposition material will pass during an electroplating operation on its way from a distal anode to a deposition surface. In either approach, it is possible for CC masks to share a common support, i.e. the patterns of conformable dielectric material for plating multiple layers of material may be located in different areas of a single support structure. When a single support structure contains multiple plating patterns, the entire structure is referred to as the CC mask while the individual plating masks may be referred to as “submasks”. In the present application such a distinction will be made only when relevant to a specific point being made.

In preparation for performing the selective deposition of the first operation, the conformable portion of the CC mask is placed in registration with and pressed against a selected portion of the substrate (or onto a previously formed layer or onto a previously deposited portion of a layer) on which deposition is to occur. The pressing together of the CC mask and substrate occur in such a way that all openings, in the conformable portions of the CC mask contain plating solution. The conformable material of the CC mask that contacts the substrate acts as a barrier to electrodeposition while the openings in the CC mask that are filled with electroplating solution act as pathways for transferring material from an anode (e.g. the CC mask support) to the non-contacted portions of the substrate (which act as a cathode during the plating operation) when an appropriate potential and/or current are supplied.

An example of a CC mask and CC mask plating are shown in FIGS. 1A-1C. FIG. 1A shows a side view of a CC mask 8 consisting of a conformable or deformable (e.g. elastomeric) insulator 10 patterned on an anode 12. The anode has two functions. One is as a supporting material for the patterned insulator 10 to maintain its integrity and alignment since the pattern may be topologically complex (e.g., involving isolated “islands” of insulator material). The other function is as an anode for the electroplating operation. FIG. 1A also depicts a substrate 6 separated from mask 8. CC mask plating selectively deposits material 22 onto a substrate 6 by simply pressing the insulator against the substrate then electrodepositing material through apertures 26 a and 26 b in the insulator as shown in FIG. 1B. After deposition, the CC mask is separated, preferably non-destructively, from the substrate 6 as shown in FIG. 1C. The CC mask plating process is distinct from a “through-mask” plating process in that in a through-mask plating process the separation of the masking material from the substrate would occur destructively. As with through-mask plating, CC mask plating deposits material selectively and simultaneously over the entire layer. The plated region may consist of one or more isolated plating regions where these isolated plating regions may belong to a single structure that is being formed or may belong to multiple structures that are being formed simultaneously. In CC mask plating, as individual masks are not intentionally destroyed in the removal process, they may be usable in multiple plating operations.

Another example of a CC mask and CC mask plating is shown in FIGS. 1D-1G. FIG. 1D shows an anode 12′ separated from a mask 8′ that comprises a patterned conformable material 10′ and a support structure 20. FIG. 1D also depicts substrate 6 separated from the mask 8′. FIG. 1E illustrates the mask 8′ being brought into contact with the substrate 6. FIG. 1F illustrates the deposit 22′ that results from conducting a current from the anode 12′ to the substrate 6. FIG. 1G illustrates the deposit 22′ on substrate 6 after separation from mask 8′. In this example, an appropriate electrolyte is located between the substrate 6 and the anode 12′ and a current of ions coming from one or both of the solution and the anode are conducted through the opening in the mask to the substrate where material is deposited. This type of mask may be referred to as an anodeless INSTANT MASK™ (AIM) or as an anodeless conformable contact (ACC) mask.

Unlike through-mask plating, CC mask plating allows CC masks to be formed completely separate from the fabrication of the substrate on which plating is to occur (e.g. separate from a three-dimensional (3D) structure that is being formed). CC masks may be formed in a variety of ways, for example, a photolithographic process may be used. All masks can be generated simultaneously prior to structure fabrication rather than during it. This separation makes possible a simple, low-cost, automated, self-contained, and internally-clean “desktop factory” that can be installed almost anywhere to fabricate 3D structures, leaving any required clean room processes, such as photolithography to be performed by service bureaus or the like.

An example of the electrochemical fabrication process discussed above is illustrated in FIGS. 2A-2F. These figures show that the process involves deposition of a first material 2 which is a sacrificial material and a second material 4 which is a structural material. The CC mask 8, in this example, includes a patterned conformable material (e.g. an elastomeric dielectric material) 10 and a support 12 which is made from deposition material 2. The conformal portion of the CC mask is pressed against substrate 6 with a plating solution 14 located within the openings 16 in the conformable material 10. An electric current, from power supply 18, is then passed through the plating solution 14 via (a) support 12 which doubles as an anode and (b) substrate 6 which doubles as a cathode. FIG. 2A, illustrates that the passing of current causes material 2 within the plating solution and material 2 from the anode 12 to be selectively transferred to and plated on the substrate 6. After electroplating the first deposition material 2 onto the substrate 6 using CC mask 8, the CC mask 8 is removed as shown in FIG. 2B. FIG. 2C depicts the second deposition material 4 as having been blanket-deposited (i.e. non-selectively deposited) over the previously deposited first deposition material 2 as well as over the other portions of the substrate 6. The blanket deposition occurs by electroplating from an anode (not shown), composed of the second material, through an appropriate plating solution (not shown), and to the cathode/substrate 6. The entire two-material layer is then planarized to achieve precise thickness and flatness as shown in FIG. 2D. After repetition of this process for all layers, the multi-layer structure 20 formed of the second material 4 (i.e. structural material) is embedded in first material 2 (i.e. sacrificial material) as shown in FIG. 2E. The embedded structure is etched to yield the desired device, i.e. structure 20, as shown in FIG. 2F.

Various components of an exemplary manual electrochemical fabrication system 32 are shown in FIGS. 3A-3C. The system 32 consists of several subsystems 34, 36, 38, and 40. The substrate holding subsystem 34 is depicted in the upper portions of each of FIGS. 3A to 3C and includes several components: (1) a carrier 48, (2) a metal substrate 6 onto which the layers are deposited, and (3) a linear slide 42 capable of moving the substrate 6 up and down relative to the carrier 48 in response to drive force from actuator 44. Subsystem 34 also includes an indicator 46 for measuring differences in vertical position of the substrate which may be used in setting or determining layer thicknesses and/or deposition thicknesses. The subsystem 34 further includes feet 68 for carrier 48 which can be precisely mounted on subsystem 36.

The CC mask subsystem 36 shown in the lower portion of FIG. 3A includes several components: (1) a CC mask 8 that is actually made up of a number of CC masks (i.e. submasks) that share a common support/anode 12, (2) precision X-stage 54, (3) precision Y-stage 56, (4) frame 72 on which the feet 68 of subsystem 34 can mount, and (5) a tank 58 for containing the electrolyte 16. Subsystems 34 and 36 also include appropriate electrical connections (not shown) for connecting to an appropriate power source (not shown) for driving the CC masking process.

The blanket deposition subsystem 38 is shown in the lower portion of FIG. 3B and includes several components: (1) an anode 62, (2) an electrolyte tank 64 for holding plating solution 66, and (3) frame 74 on which feet 68 of subsystem 34 may sit. Subsystem 38 also includes appropriate electrical connections (not shown) for connecting the anode to an appropriate power supply (not shown) for driving the blanket deposition process.

The planarization subsystem 40 is shown in the lower portion of FIG. 3C and includes a lapping plate 52 and associated motion and control systems (not shown) for planarizing the depositions.

In addition to teaching the use of CC masks for electrodeposition purposes, the '630 patent also teaches that the CC masks may be placed against a substrate with the polarity of the voltage reversed and material may thereby be selectively removed from the substrate. It indicates that such removal processes can be used to selectively etch, engrave, and polish a substrate, e.g., a plaque.

The '630 patent provides various examples of useful planarization methods. These examples include mechanical (e.g., diamond lapping and silicon carbide lapping), chemical-mechanical, and non-mechanical (e.g., electrical discharge machining) planarization processes.

Further teachings of the '630 patent indicate that diamond lapping can be performed using a single grade of diamond abrasive, e.g., about 1-6 micron, or diamond abrasives of various grades. Lapping with different grades of abrasive can be performed using separate lapping plates, or in different regions of a single plate. For example, a coarse diamond abrasive can be applied to the outer region of a spinning circular lapping plate, and a fine diamond abrasive can be applied to the inner region. A removable circular wall can be provided between the inner and outer regions to increase segregation. The layer to be planarized first contacts the outer region of the plate, then is optionally rinsed to remove coarse abrasive, and then is moved to the inner region of the plate. The planarized surface can then be rinsed using a solution, e.g., water-based or electrolyte-based solution, to remove both abrasive and abraded particles from the planarized layer. The abrasive slurry preferably is easily removable, e.g., water-soluble. Layer thickness, planarity and smoothness can be monitored, e.g., using an optical encoder, wear resistant stops, and by mating the layer under a known pressure with a precision flat metal plate and measuring the resistance across the plate-layer junction.

The '630 patent further provides an examples of a preferred planarization processes. One includes allowing the work piece, i.e., the substrate having the layer to be planarized, to rotate within a “conditioning ring” on the lapping plate. Another involves lapping being performed by moving a workpiece around the surface of a lapping plate using the X/Y motion stages of an electroplating apparatus without rotating or releasing the workpiece.

A need remains for improved electrochemical fabrication methods and apparatus that provide needed surface quality while optimizing production time. A need also remains for improved electrochemical fabrication methods and apparatus that provide different surface quality for different regions of a structure that is being formed.

SUMMARY OF THE INVENTION

It is an object of certain aspects of the invention to provide an improved electrochemical fabrication process or apparatus that provides needed surface quality without wasting production time.

It is an object of certain aspects of the invention to provide an improved electrochemical fabrication process or apparatus that provides different surface qualities for different regions of a structure.

Other objects and advantages of various aspects of the invention will be apparent to those of skill in the art upon review of the teachings herein. The various aspects of the invention, set forth explicitly herein or otherwise ascertained from the teachings herein, may address any one of the above objects alone or in combination, or alternatively may not address any of the objects set forth above but instead address some other object ascertained from the teachings herein. It is not intended that all of these objects be addressed by any single aspect of the invention even though that may be the case with regard to some aspects.

In a first aspect of the invention an electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers, includes (A) supplying a plurality of preformed masks, wherein each mask includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein each mask includes a support structure that supports the patterned conformable dielectric material; (B) selectively depositing at least a portion of a layer onto the substrate, wherein the substrate may include previously deposited material; (C) forming a plurality of layers such that each successive layer is formed adjacent to and adhered to a previously deposited layer, wherein said forming includes repeating operation (B) a plurality of times; wherein at least a plurality of the selective depositing operations include(1) contacting the substrate and the conformable material of a selected preformed mask; (2) in presence of a plating solution, conducting an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) separating the selected preformed mask from the substrate; and (D) removing material deposited on at least one layer using a first removal process that includes one or more operations having one or more parameters; and (E) removing material deposited on at least one different layer using a second removal process that includes one or more operations having one or more parameters, wherein the first removal process differs from the second removal process by inclusion of at least one different operation or at least one different parameter.

In a second aspect of the invention an electrochemical fabrication apparatus for producing a three-dimensional structure from a plurality of adhered layers, includes (A) a plurality of preformed masks, wherein each mask includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein each mask includes a support structure that supports the patterned conformable dielectric material; (B) means for selectively depositing at least a portion of a layer onto the substrate, wherein the substrate may include previously deposited material; (C) means for forming a plurality of layers such that each successive layer is formed adjacent to and adhered to a previously deposited layer, wherein said forming includes repeating operation (B) a plurality of times; wherein the means for selectively depositing includes (1) means for contacting the substrate and the conformable material of a selected preformed mask; (2) means for conducting, in presence of a plating solution, an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) means for separating the selected preformed mask from the substrate; and (D) means for removing material deposited on at least one layer using a first removal process that includes one or more operations having one or more parameters; and (E) means for removing material deposited on at least one different layer using a second removal process that includes one or more operations having one or more parameters, wherein the first removal process differs from the second removal process by inclusion of at least one different operation or at least one different parameter.

In a third aspect of the invention an electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers includes (A) selectively depositing at least a portion of a layer onto a substrate, wherein the substrate may include previously deposited material; (B) forming a plurality of layers such that each successive layer is formed adjacent to and adhered to a previously deposited layer; (C) removing material deposited on at least one layer using a first removal process that includes one or more operations having one or more parameters; and (E) removing material deposited on at least one different layer using a second removal process that includes one or more operations having one or more parameters, wherein the first removal process differs from the second removal process by inclusion of at least one different operation or at least one different parameter.

In a fourth aspect of the invention an electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers, the process including: (A) forming at least a portion of a layer by either selectively depositing a material, to form portion of a layer, onto a substrate or by selectively etching into a previously deposited material that occupies at least a portion of a layer and then depositing a material into an opening formed by the selective etching, wherein the substrate may include previously deposited layers of material; (B) forming a plurality of layers such that subsequent layers are formed adjacent to and adhered to previously deposited layers; (C) finishing a surface of at least a portion of one or more materials deposited on at least one layer using a first process that includes one or more operations having one or more parameters; and (E) finishing a surface of at least a portion of one or more materials deposited on the at least one layer using a second process that includes one or more operations having one or more parameters, wherein the portions subject to the first and second processes are not identical and wherein the first process differs from the second process by inclusion of at least one different operation, removal of at least one operation, or use of at least one different parameter value.

In a fifth aspect of the invention an electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers, the process including: (A) forming at least a portion of a layer by either selectively depositing a material, to form portion of a layer, onto a substrate or by selectively etching into a previously deposited material that occupies at least a portion of a layer and then depositing a material into an opening formed by the selective etching, wherein the substrate may include previously deposited layers of material; (B) forming a plurality of layers such that subsequent layers are formed adjacent to and adhered to previously deposited layers; (C) finishing a surface of at least a portion of one or more materials deposited on at least one layer using a first process that includes one or more operations having one or more parameters; and (E) finishing a surface of at least a portion of one or more materials deposited on at least one different layer using a second process that includes one or more operations having one or more parameters, wherein the first process differs from the second process by inclusion of at least one different operation, removal of at least one operation, or use of at least one different parameter value.

Other aspects of the invention will be understood by those of skill in the art upon reviewing the teachings herein. Other aspects of the invention may involve apparatus that can be used in implementing one or more of the above method aspects of the invention. These other aspects of the invention may involve various combinations of the aspects presented above, addition of various features of one or more embodiments, as well as other configurations, structures, functional relationships, and processes that have not been specifically set forth above.

In some embodiments, electrochemical fabrication processes produce one or more three-dimensional structures (e.g. components or devices) from a plurality of layers of deposited materials wherein the formation of at least some portions of some layers are produced by operations that remove material, redistribute, condition, or otherwise finish selected surfaces of a deposited material. In some embodiments, removal, redistribution, conditioning, or finishing operations are varied between layers or between different portions of a layer such that different surface qualities are obtained. In other embodiments varying surface quality may be obtained without varying selected removal, redistribution or finishing operations or parameters but instead by relying on differential interaction between removal or conditioning operations and different materials encountered by these operations.

In some embodiments a finishing process (e.g. removal or conditioning process) on a 1st layer differs from a removal or conditioning process on a 2nd layer. In some more focused embodiments the finishing process used on a 1st layer includes an operation not used in the finishing process used on a 2nd layer. In some other more focused embodiments, the finishing process on a 2nd layer includes an operation not used in the finishing process on the 1st layer. In some other embodiments the finishing process on the 1st layer includes a parameter which is different from a parameter used in the finishing process on the 2nd layer.

In some embodiments a finishing process (e.g. removal or conditioning process) used on a 1st portion of a layer differs from the finishing process used on a 2nd portion of the layer. In some more focused embodiments, the finishing process used on the 1st portion includes an operation not used in the finishing process used on the 2nd portion. In some more focused embodiments, the finishing process used on the 2nd portion includes an operation not used in the finishing process used on the 1st portion. In some other embodiments, the finishing process used on the 1st portion includes a parameter which is different from a parameter used in the finishing process used on the 2nd portion.

In some embodiments a selected finishing process (e.g. removal or conditioning process) is used on only a portion of a layer. In some more focused embodiments the process is limited to operating on one or more selected materials. In some more focused embodiments the process is limited to operating on one or more selected portions of one or more selected materials. In some other more focused embodiments, the process is limited so as not to operate on one or more selected portions of one or more selected materials. In some additional embodiments a mask having a pattern of openings corresponding to a pattern of a selected material forming a portion of the layer is used to define a surface on which the process will operate. In some further embodiments a mask having a pattern of openings corresponding to non-outward facing surfaces of a selected material forming a portion of the layer is used to define the surface on which the process will operate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C schematically depict side views of various stages of a CC mask plating process, while FIGS. 1D-1G schematically depict side views of various stages of a CC mask plating process using a different type of CC mask.

FIGS. 2A-2F schematically depict side views of various stages of an electrochemical fabrication process as applied to the formation of a particular structure where a sacrificial material is selectively deposited while a structural material is blanket deposited.

FIGS. 3A-3C schematically depict side views of various example subassemblies that may be used in manually implementing the electrochemical fabrication method depicted in FIGS. 2A-2F.

FIGS. 4A-4F schematically depict the formation of a first layer of a structure using adhered mask plating where the blanket deposition of a second material overlays both the openings between deposition locations of a first material and the first material itself

FIG. 4G depicts the completion of formation of the first layer resulting from planarizing the deposited materials to a desired level.

FIG. 5 depicts a flowchart of the generalized process of some embodiments of the instant invention.

FIGS. 6A and 6B depict a CAD design of a scanning micro-mirror and an electrochemically fabricated structure according to that design, respectively.

FIGS. 7A-7H set forth a side view (FIG. 7A) of a six layer structure as well as top views (FIGS. 7B-7H) of the substrate and of each layer of that structure.

FIGS. 8A-8H illustrate a side view (FIG. 8A) and top views (FIGS. 8B-8H) of the structure of FIGS. 7A-7H where each of four distinct regions for each layer are illustrated.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1A-1G, 2A-2F, and 3A-3C illustrate various features of one form of electrochemical fabrication. Other electrochemical fabrication techniques are set forth in the '630 patent referenced above, in the various previously incorporated publications, in various other patents and patent applications incorporated herein by reference. Still others may be derived from combinations of various approaches described in these publications, patents, and applications, or are otherwise known or ascertainable by those of skill in the art from the teachings set forth herein. All of these techniques may be combined with those of the various embodiments of the invention to yield enhanced embodiments. Still other embodiments may be derived from combinations of the various embodiments explicitly set forth herein.

FIGS. 4A-4F illustrate various stages in the formation of a single layer of a multi-layer fabrication process where a second metal is deposited on a first metal as well as in openings in the first metal so that the first and second metal form part of the layer. In FIG. 4A a side view of a substrate 82 is shown onto which patternable photoresist 84 is cast as shown in FIG. 4B. In FIG. 4C a pattern of resist is shown that results from the curing, exposing, and developing of the resist. The patterning of the photoresist 84 results in openings or apertures 92(a)-92(c) extending from a surface 86 of the photoresist through the thickness of the photoresist to surface 88 of the substrate 82. In FIG. 4D a metal 94 (e.g. nickel) is shown as having been electroplated into the openings 92(a)-92(c). In FIG. 4E the photoresist has been removed (i.e. chemically stripped) from the substrate to expose regions of the substrate 82 which are not covered with the first metal 94. In FIG. 4F a second metal 96 (e.g. silver) is shown as having been blanket electroplated over the entire exposed portions of the substrate 82 (which is conductive) and over the first metal 94 (which is also conductive). FIG. 4G depicts the completed first layer of the structure which has resulted from the planarization of the first and second metals down to a height that exposes the first metal and sets a thickness for the first layer.

In some preferred embodiments of the invention electrochemical fabrication processes or apparatus are provided that include enhanced removal or finishing processes and apparatus. In particular the enhanced removal or finishing processes involve use of one or more different removal of finishing operations and/or one or more different removal or finishing parameters on at least two different layers. The use of one process may allow faster, or otherwise preferred, removal or finishing operations to occur for selected layers (e.g. when surface quality is not critical) while a slower process may be used, or an otherwise less preferred removal or finishing process, when surface quality is more critical. Thus, the use of different definable removal processes allows process optimization to occur.

In other embodiments different finishing operations may be used on different parts of a single layer or on different layers simply to obtain a desired difference in surface finish regardless of the overall processing time.

A flow chart depicting the general electrochemical fabrication process for some embodiments of the invention is depicted in FIG. 5. Element 102 depicts the beginning of the process while element 104 sets the layer number variable “i”, to a value of one. Decision block 106 inquires as to whether or not the layer number variable “i” has exceeded the total number of layers “N” for the structure being formed. If so, the process proceeds to and ends at element 108. Assuming the variable “i” has not exceeded the total number of layers “N”, the process proceeds to element 112 which sets the deposition number variable “j” for layer “i” to a value of one. Next, element 114 calls for the deposition of the material associated with deposition number “j” for layer “i”. Next, element 116 increments the deposition number by one. After which, element 118 inquires as to whether or not the deposition number exceeds the maximum number of depositions “M” associated with layer “i”. If not, the process loops back to element 114 and the next deposition for layer “i” is performed. If “yes”, the process moves forward to element 122 where the finishing process (e.g. removal, redistribution, or conditioning process) operation variable “k” is set to a value of 1. Next the process moves to element 124 where the finishing process “k” is performed for layer “i”. The finishing process “k” associated with any given layer “i” may or may not exist. If it exists it may involve an identical operation or parameters that were used on other layers, it may involve a different operation from that used on one or more layers, or it may involve a similar operation used on other layers but with different associated parameters. After performance of removal process “k” for layer “i”, the process proceeds to element 126 where an inquiry is made as to whether or not the value of “k” equals the maximum number of finishing operations “P” associated with layer “i”. If it does not, “k” is incremented by one (element 128) and the process loops back to element 124 for performing the next removal operation for layer “i”. If “k” does equal “P”, the layer value “i” is incremented by 1 as indicated by element 132 and the process loops back to element 106. The value of “N”, the value of “M” for each layer “i”, the value of “P” for each layer “i”, the deposition processes associated with variable “j” for each layer “i”, and the finishing processes (i.e. operations and parameters) associated with variable “k” for each layer “i” can be held in the mind of an operator when a manual fabrication process is being used or they may be set in a look up table, determined or specified via a calculation, or otherwise determined and specified for use by an automated apparatus.

In some preferred embodiments of the present invention either the value of variable “k” is different between at least two layers and/or the operations or parameters associated with a given value of “k” for at least two different layers are different.

For example, on one layer where surface finish is not critical, a single relatively course abrasive may be used in a single lapping process to remove material and planarize the layer whereas on a different layer two or more lapping processes may be used where progressively finer abrasives may be used to yield a smoother surface than would be obtained in the single removal operation. In an alternative process, a single lapping operation may be used on two different layers but one of the layers may additionally involve a buffing process or a polishing process such as CMP. In a further alternative, lapping or CMP may be used on two different layers but the parameters under which the operations operate may be changed.

In certain embodiments it may be desirable to use a finer abrasive to bring the layer to a desired level and then use a courser abrasive for a short period of time to roughen the surface without significantly changing its effective surface level. More generally, in some circumstances operations and parameters may be chosen so that certain layers are provided with a higher degree of smoothness while in other circumstances, operations and parameters are chosen to provide a course surface without significantly causing the level or height of the material to deviate from a desired level or height.

If a mirror like surface were desired for a given layer, more time or cost could be spent on the finishing operation (e.g. planarization operation and polishing operation) for that specific layer while allowing all other layers to undergo a faster or otherwise more acceptable process. The layer or layers that undergo a more rigorous, difficult, costly, or time consuming removal process may include the last layer of the structure, an initial layer of the structure, or may be limited to one or more intermediate layers.

If at least two different materials are being used in the deposition process, e.g. at least one sacrificial material and at least one structural material, then surface quality may be imparted either directly or indirectly by the finishing process. If the desired surface (i.e. the surface that is to have the desired attributes) is one that is being operated on by the removal process (e.g. planarized), the removal process imparts the quality to the surface directly and if the surface is associated with layer “i” then these removal operations are performed on layer “i”. If on the other hand, the desired surface is not one that is being planarized, then the quality of it is being imparted from the surface on which it was formed or will be formed (e.g. from the planarization provided to the previously formed layer). In this latter case, if the surface for which the particular quality is being sought is associated with layer “i” then it is layer “i−1” that must receive the specialized removal process. In other words if a structure is being formed by stacking layers one on top of the other, it is the up-facing surfaces of each layer that undergo removal, it is the up-facing surfaces that obtain their surface qualities directly form the removal operations whereas the down-facing surfaces pick up their surface qualities as a result of the surface quality that was achieved on the previously formed layer. If the layers are being added below previously formed layers then roles of the up-facing and down-facing surfaces are reversed.

In other embodiments, finishing may be performed at least in part using etchants that may be substantially non-selective with respect to their ability to etch materials being used in the formation of the structure or they may offer a significant level of selectivity for enhanced etching of one material relative to another. In still other embodiments electrochemical etching or polishing may be used during some or all finishing operations. In still other embodiments, finishing operations may involve a combined use of one or more etchants, mechanical operations, grinding or polishing operations, application of electrical currents or potentials, and the like.

The CAD design of a scanning micro-mirror device that can benefit from various embodiments of the invention is depicted in FIG. 6A while a mirror formed from that CAD file using an electrochemical fabrication process is shown in the SEM of FIG. 6B. The quality of the formed mirror and particularly the surface quality of the upper surface of the reflective portion 200 of the mirror may benefit from the enhanced fabrication techniques of various embodiments of the present invention. In these embodiments, the layer containing the upper surface of the mirror may undergo polishing operations which are not performed on other layers of the structure which can produce a mirror of desired reflectivity while not hindering the overall build process with such a high level of polishing on each layer.

In some embodiments, the selective application of specialized surface finishing may provide not only smoother surfaces when desired but also rougher surfaces or surfaces with other qualities when appropriate. For example, in some applications adhesion between successive layers may be enhanced by roughening the surface prior to deposition of the structural material associated with the next layer. In still other embodiments, significantly roughing or otherwise treating the surface may decrease undesirable spectral reflections from that surface. For example in FIG. 6B, it may be desirable to roughen or otherwise treat surfaces 202, 204, 206, 208, 210 and 212 to decrease such reflections. If one or more of these additional surfaces exist on the same layer where other finishing processes are desired (such as for surfaces 200, 204, 206, 208 and 210) it may be necessary to selectively perform two or more finishing processes independently of one another. Alternatively, it may be possible to perform a first finishing process in a blanket manner with the subsequent processes formed in selective manners where the result of the first finishing process is simply the starting point for the subsequent operations. Of course, those of skill in the art will understand that other levels of processing selectivity or processing order are possible. For example, if a first selectively applied finishing process creates a great disparity between surface finishes of two distinct regions then a common blanket finishing operation may be used which still leaves a desired level of disparity between relevant attributes of the distinct regions. As a further example, after an initial planarization operation brings a given layer to a desired level and to a desired surface finish, a thin blank deposition or selective deposition of a desired coating material may be made, after which additional selective or blanket finishing operations may be used to take the entire surface or a portion of the surface to a final finished state.

In some embodiments it may be desirable to select, or tailor, the surface finish associated with a given portion of a layer depending on how that portion relates to the presence or lack of presence of structural material in the same area on a subsequent layer that is to be formed. In other embodiments, similar consideration of sacrificial materials may be used.

In some embodiments a single structural material will be used and that structural material will typically overlay at least in part, structural material deposited on a previous layer or structural material to be deposited on a subsequent layer. In these embodiments, structural material on each portion of a layer may be classified into one of four categories: (1) up facing, (2) down facing, (3) both up facing and down facing, or (4) continuing. An up facing portion of structural material on a given layer is that portion of the structural material that is not bounded by structural material that is associated with the next higher layer level. A down facing region of structural material on a given layer is that portion of the structural material that is not bounded from below by structural material located on the layer that is located immediately below the given layer. A portion of structural material defined as both up facing and down facing is not bounded from above or bounded from below by structural material that exists on the next higher layer or on the previous lower layer, respectively. Finally, a portion of structural material located on a given layer that is bounded from below and bounded from above by structural material on the immediately succeeding layer and preceding layer, respectively, is a continuing region.

In other embodiments layers need not be stacked along a vertical axis and thus the above terms may either be defined for a different build orientation or alternatively they may simply be reinterpreted in an appropriate way. In embodiments where more than one structural material is used and/or more than one sacrificial material is used, additional or alternative distinct regions may be defined as necessary. In still other embodiments where sensitivity to certain structural features is critical, alternative or added regions may be defined. In still other embodiments where boundary effects between distinct regions, or other issues, make it desirable to define regions which are slightly larger or smaller than what is ascertainable from layer to layer comparisons alone, offset boundaries may be defined using erosion techniques or expansion techniques

FIGS. 7A-7H set forth a side view of a six layer structure as well as top views of each layer of that structure. FIG. 7A depicts a side view of a six layer structure that includes layer portions that are definable in each of the four distinct categories noted above. For simplicity sake, the structure is assumed to be formed by stacking layers on top of one another starting with the first layer 301 formed on top of a substrate 300 followed by layers 302 to 306. Each layer comprises a portion that is formed of structural material 314 and a portion formed from a sacrificial material 316. A top view of the substrate 300 is shown is FIG. 7B. The regions of structural material on layer 301 are shown in FIG. 7C relative to an outline 310 of the substrate. FIGS. 7D-7H show structural material associated with layers 302 to 306, respectively, relative to an outline 310 of substrate 300.

FIGS. 8A-8H illustrate a side view and top views of the structure of FIGS. 7A-7H where each of the four distinct regions for each layer are illustrated. FIG. 8A shows that a structure 308 is formed on a substrate 300 from layers 301 to layers 306. FIG. 8A also indicates that different portions of each layer can be classified into the different regions discussed above (where like regions are designated with like fill patterns). It can be seen that continuing regions 322 exist on some layers, regions that are both up facing and down facing 324 exist on some layers, regions that are down facing only 326 exist on some layers, and regions that are up facing only 328 exist on some layers. FIGS. 8B-8H illustrate top views of the substrate and each of layers 301 through 306, respectively, where distinct regions 322, 324, 326, and 328 are shown with fill patterns similar to those illustrated in FIG. 8A.

The recognition of distinct portions (or regions) of layers may be used in tailoring finishing processes that may be used in achieving desired surface finishes for each portion of each layer. In some alternative embodiments, if desired, sacrificial material may also receive similar designations which may be used for determining additional or alternative surface finishing processes that may be used.

Once the distinct regions of each layer are determined, an associated desired surface quality parameter may be associated with each region. From the combined surface quality parameters associated with each layer appropriate surface finishing or treatment processes may be proposed and an order for performance proposed. From an analysis of the proposed processes and order, conflicts may be determined and either removed by process or order modifications or alternatively by deciding to use fall back or compromise finishing processes.

In some embodiments where structures will be formed by stacking layers one above the other, it may be appropriate to associate portions of a next layer (n+1) that are down-facing with the previous layer (n) so that appropriate finishing operations may be used on at least portions of the sacrificial material so that those portions have appropriate surface finish after forming the previous layer (n) which will be used in setting the surface quality of the down-facing features of structural material on the next layer (n+1). In embodiments with other build orientations (e.g. subsequent layers formed below previously formed layers) other appropriate associations may be made.

As an example of how different surface finishes may be applied to a single layer one may consider layer 304 of FIG. 8F. In this layer it may be seen that a portion of the structural material is continuing 322 and a portion is up-facing 328 or 324. If it is desired that up facing surfaces have a relatively smooth surface finish and that non-up-facing regions may have an alternative surface finish (e.g. one which is formed faster or one which is intentionally roughened up to, for example, enhance adhesion between layers), the entire layer may be planarized or polished to the extent desired to obtain the surface finish to be associated with up-facing features (assuming any exist on the layer being considered) then a contact mask or other mask may be placed against the resulting surface. The solid portions of the mask may be pressed against the portion of the surface(s) that are to retain the desired “up-facing” finish and the openings in the mask may be located over those portions of the surface(s) that are intended to have a different finish (e.g. rougher finish). The exposed surface(s) may be treated with an appropriate chemical etch, electrochemical etch, reactive or inactive material bombardment, radiation bombardment, or the like which is intended to produce the desired surface finish. After appropriate selective treatment, the mask may be removed. The operations to produce the surface finish may or may not significantly change the level of the exposed surface.

In other embodiments where a third distinct surface finish is desired a further mask of selected configuration may be placed on or contacted to the surface leaving openings in the regions to be treated. The selective treatment may be applied after which the mask may be removed. In still other embodiments surface treatments that are performed may include deposition operations or redistribution operations (e.g. alternate etchings and depositions) as opposed to, or in addition to, the removal operations.

The method embodiments of the present invention may be implemented manually or via an automated or semi-automated apparatus. The apparatus used for either manual or automated execution of the methods may involve appropriate deposition stations (e.g. one or more selective deposition stations and one or more blanket deposition stations), one or more layer finishing or removal stations set up or modifiable to implement the specific type of removal operations to be performed, capability to monitor deposit height or level during removal operations or between removal operations, one or more cleansing or activation stations, one or more inspection stations. Various apparatus configurations are within the skill of the art based on the teachings herein. A number of alternatives are disclosed in the previously referenced and incorporated '630 patent.

Preferred apparatus for implementing the present invention will involve one or more programmed computers that control the process flow and associated operations and parameters.

Various other embodiments of the present invention exist. Some of these embodiments may be based on a combination of the teachings herein with various teachings incorporated herein by reference. Some embodiments may not use any blanket deposition process. Some embodiments may involve the selective deposition of a plurality of different materials on a single layer or on different layers. Some embodiments may use blanket depositions processes that are not electrodeposition processes. Some embodiments may use selective deposition processes on some layers that are not electrodeposition processes. Some embodiments may use nickel as a structural material while other embodiments may use different materials such as gold, silver, or any other electrodepositable materials that can be separated from a sacrificial material such as copper. Some embodiments may use copper as the structural material with or without a sacrificial material. Some embodiments may remove a sacrificial material while other embodiments may not. In some embodiments, the depth of deposition will be enhanced by pulling a conformable contact mask away from the substrate as deposition is occurring in a manner that allows the seal between the conformable portion of the CC mask and the substrate to shift from the face of the conformal material to the inside edges of the conformable material. In some embodiments, manual or automated visual inspection of a deposits or planarized surfaces may occur.

In view of the teachings herein, many further embodiments, alternatives in design and uses of the instant invention will be apparent to those of skill in the art. As such, it is not intended that the invention be limited to the particular illustrative embodiments, alternatives, and uses described above but instead that it be solely limited by the claims presented hereafter. 

1. An electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers, the process comprising: (A) forming at least a portion of a layer by either selectively depositing a material, to form portion of a layer, onto a substrate or by selectively etching into a previously deposited material that occupies at least a portion of a layer and then depositing a material into an opening formed by the selective etching, wherein the substrate may comprise previously deposited layers of material; (B) forming a plurality of layers such that subsequent layers are formed adjacent to and adhered to previously deposited layers; (C) finishing a surface of at least a portion of one or more materials deposited on at least one layer using a first process that comprises one or more operations having one or more parameters; and (E) finishing a surface of at least a portion of one or more materials deposited on at least one different layer using a second process that comprises one or more operations having one or more parameters, wherein the first process differs from the second process by inclusion of at least one different operation, removal of at least one operation, or use of at least one different parameter value.
 2. The process of claim 1 wherein a determination of a finishing operation or parameter for finishing at least one layer or of the at least one different layer is at least in part determined from a relationship between portions of one layer and portions of an adjacent layer.
 3. The process of claim 1 wherein a mask is used to define at least one opening which exposes a surface that is to undergo a selected finishing operation and where unexposed portions of the surface define a portion of the surface that is not to undergo the selected finishing operation.
 4. The process of claim 2 wherein the relationship involves a determination of whether portions of a structural material are outward facing.
 5. The process of claim 4 wherein the outward facing portion is up-facing and a build orientation comprises forming subsequent layers above previously formed layers.
 6. The process of claim 4 wherein the outward facing portion is down-facing and a build orientation comprises forming subsequent layers above previously formed layers.
 7. The process of claim 4 wherein the outward facing portion is up-facing and a build orientation comprises forming subsequent layers below previously formed layers.
 8. The process of claim 4 wherein the outward facing portion is down-facing and a build orientation comprises forming subsequent layers below previously formed layers.
 9. An electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers, the process comprising: (A) forming at least a portion of a layer by either selectively depositing a material, to form portion of a layer, onto a substrate or by selectively etching into a previously deposited material that occupies at least a portion of a layer and then depositing a material into an opening formed by the selective etching, wherein the substrate may comprise previously deposited layers of material; (B) forming a plurality of layers such that subsequent layers are formed adjacent to and adhered to previously deposited layers; (C) finishing a surface of at least a portion of one or more materials deposited on at least one layer using a first process that comprises one or more operations having one or more parameters; and (E) finishing a surface of at least a portion of one or more materials deposited on the at least one layer using a second process that comprises one or more operations having one or more parameters, wherein the portions subject to the first and second processes are not identical and wherein the first process differs from the second process by inclusion of at least one different operation, removal of at least one operation, or use of at least one different parameter value.
 10. The process of claim 9 wherein the first process acts upon a portion of the at least one layer and the second process acts upon a portion of the at least one layer that includes a region not acted upon by the first process.
 11. The process of claim 9 wherein the first process acts upon a portion of the at least one layer and the second process acts upon a portion of the at least one layer that is exclusive of the portion acted upon by the first process.
 12. The process of claim 9 a determination of which portion of the at least one layer is to be undergo finishing using the first process or using the second process is at least in part determined from a relationship between portions of the at least one layer and portions of an adjacent layer.
 13. The process of claim 9 wherein a mask is used to define at least one opening which exposes a surface that is to undergo a selected finishing operation and where unexposed portions of the surface define a portion of the surface that is not to undergo the selected finishing operation.
 14. The process of claim 10 wherein the relationship involves a determination of whether portions of a structural material are outward facing.
 15. The process of claim 14 wherein the outward facing portion is up-facing and a build orientation comprises forming subsequent layers above previously formed layers.
 16. The process of claim 14 wherein the outward facing portion is down-facing and a build orientation comprises forming subsequent layers above previously formed layers.
 17. The process of claim 14 wherein the outward facing portion is up-facing and a build orientation comprises forming subsequent layers below previously formed layers.
 18. The process of claim 14 wherein the outward facing portion is down-facing and a build orientation comprises forming subsequent layers below previously formed layers.
 19. The process of claim 14 wherein the relationship involves a determination of whether portions of a structural material continue from one layer to a subsequent layer.
 20. The process of claim 14 wherein the relationship involves a determination of whether portions of a sacrificial material continue from one layer to a subsequent layer. 